title: Alternative diagnosis to heparin-induced thrombocytopenia in two critically ill patients despite a positive PF4/heparin-antibody test.
abstract: Thrombocytopenia can cause diagnostic challenges in patients who have received heparin. Heparin-induced thrombocytopenia (HIT) is often considered in the differential diagnosis, and a positive screening can be mistaken as confirmation of the disorder. We present two patients who both received low-molecular-weight heparin for several days. In the first patient, clinical judgment rejected the suspicion of HIT despite a positive screening assay, and treatment for the alternative diagnosis of post-transfusion purpura was correctly initiated. In the second patient, the inaccurate diagnosis HIT was pursued due to a positive screening assay, while the alternative diagnosis of drug-dependent thrombocytopenia caused by piperacillin/tazobactam was rejected. This resulted in re-exposure to piperacillin/tazobactam which caused a second episode of severe thrombocytopenia. A positive screening assay for platelet factor 4/heparin-antibody should be verified by a functional assay, especially in patients with low pretest probability for HIT.
authors.affiliation: Abteilung für Transfusionsmedizin, Institut für Immunologie und Transfusionsemedizin, Ernst-Moritz-Arndt University Greifswald , Germany.
authors.forename: Gregor
authors.initials: G
authors.lastname: Hron
authors.forename: Folke
authors.initials: F
authors.lastname: Knutson
authors.forename: Thomas
authors.initials: T
authors.lastname: Thiele
authors.forename: Karina
authors.initials: K
authors.lastname: Althaus
authors.forename: Christoph
authors.initials: C
authors.lastname: Busemann
authors.forename: Sigrun
authors.initials: S
authors.lastname: Friesecke
authors.forename: Andreas
authors.initials: A
authors.lastname: Greinacher
authors.forename: Norbert
authors.initials: N
authors.lastname: Lubenow
mesh_terms: D000368:Aged; D016638:Critical Illness; D003937:Diagnosis, Differential; D004797:Enzyme-Linked Immunosorbent Assay; D005265:Femoral Neck Fractures / Q000150:complications; D006493:Heparin / Q000009:adverse effects*; D006801:Humans; D008727:Methotrexate / Q000009:adverse effects; D010198:Pancytopenia / Q000139:chemically induced; D010397:Penicillanic Acid / Q000009:adverse effects / Q000031:analogs & derivatives; D010878:Piperacillin / Q000009:adverse effects; D010976:Platelet Count; D010978:Platelet Factor 4 / Q000097:blood* / Q000276:immunology; D011696:Purpura, Thrombocytopenic / Q000139:chemically induced* / Q000175:diagnosis*; D000078142:Tazobactam; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000175:diagnosis*; D065227:Transfusion Reaction
chemical_list: D010978:Platelet Factor 4; D010397:Penicillanic Acid; D006493:Heparin; D000078142:Tazobactam; D010878:Piperacillin; D008727:Methotrexate